Cargo or carrier projectiles typically include projectile-shaped bodies, cargo, and a time fuzed ejection charge to expel the cargo during projectile flight. When exposed to flames, heat or other thermal stimuli, the most vulnerable element of this system, i.e. the expulsion charge, may reach its cook-off temperature and expel a large quantity of hazardous material from the projectile. Safety features are necessary to reduce the hazards of an accidental cook-off. Some older methods employed to protect ordnance from the effects of heat include a thermal insulation coating, used primarily on aircraft-delivered bombs, and low-temperature melt-out plugs, used primarily on certain U.S. Army projectiles. Thermal coatings are acceptable for bombs, but are not suitable for Naval guns because the coatings are susceptible to handling damage and may cause disturbances to projectile aerodynamics. Melt-out plugs are also unsuitable because they must be replaced with live fuzes just prior to firing. These replacement procedures are prohibited aboard U.S. Navy ships for safety reasons. Neither coatings nor melt-out plugs provide any significant protection for a misfire in a hot gun breech.